1. Field of the invention
The invention relates to a device and method for converting an AC voltage.
2. Related Art
For the purpose of charging laptops, computers, mobile phones and the like there is a rapidly increasing demand for compact and low-price devices for converting a mains voltage to a desired DC voltage of predetermined value, for instance 12, 24 or 36 V, optionally with flattened waveform on the DC voltage side.
U.S. Pat. No. 3,660,724 discloses an improved protective circuit wherein a silicon controlled rectifier is switched into circuit with a power supply in the presence of excessive output voltage, so as to protect the electronic equipment which is normally energized by the power supply.
DE-A-3427221 discloses a circuit in which the output voltage is compared with a reference voltage in a secondary circuit.
U.S. Pat. No. 4,272,805 discloses a switching regulator in which an input DC voltage is chopped and then applied to drive a transformer from which an AC voltage is derived which in turn is rectified in a rectifier circuit.
Existing so-called converters of the linear type are large and heavy and consume a considerable amount of power, even when no voltage is being consumed.